Virtual concatenation sequence mismatch defect detection

ABSTRACT

Methods and apparatus for identifying sequence mismatch defects associated with members of a virtual concatenation (VCAT) group are disclosed. According to one aspect of the present invention, a method for detecting sequence mismatch defects associated with a VCAT group that substantially terminates at a VCAT sink includes obtaining a first set of sequence numbers associated with the VCAT group at a first time, and determining whether a first sequence number of the first set is invalid. The method also includes identifying the first sequence number as having a sequence mismatch defect if the first sequence number is determined to be invalid.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates generally to optical networks. Morespecifically, the present invention relates to detecting sequencemismatch defects associated with virtual concatenation groups at adynamic sink.

2. Description of the Related Art

The Synchronous Optical Network (SONET) and Synchronous DigitalHierarchy (SDH) transport hierarchies provide voice and private lineservices using time division multiplexing (TDM). Within SONET and SDHtransport networks, virtual concatenation (VCAT) improves flexibilityand the efficiency.

Virtual concatenation (VCAT) is generally an inverse multiplexingtechnique that enables multiple SONET or SDH channels to besubstantially bound into a VCAT group. VCAT is defined, for example,within ITU-T G.707 and ITU-T G.783, which are each incorporated hereinby reference. A VCAT group, which includes “N” members, is effectively abyte-synchronous stream. If the VCAT group is symmetric, there are “N”receiving members of the group and “N” transmitting members of thegroup. Alternatively, if the VCAT group is asymmetric, there may be “N”receiving members of the group and any number of transmitting members ofthe group. In general, VCAT enables data, e.g., SONET or SDH payloads,to be carried in smaller bandwidth “containers” such as synchronouspayload envelopes through a network to a destination at which the datais reassembled. The smaller bandwidth containers are effectively used tocreate a higher bandwidth overall connection between two end points.

FIG. 1A is a block diagram representation of a virtual concatenation(VCAT) group within a network. Within a transport network 102, data maybe sent from a source 110 to a destination 120. It should be appreciatedthat source 110 and destination 120 are generally network elements thatsend and to receive, respectively. Source 110 and destination 120 are incommunication over a VCAT group 106 that is arranged to includedifferent paths over which data may travel at substantially the sametime.

VCAT group 106, as shown in FIG. 1B, includes a VCAT source 132 and aVCAT receiver or sink 134. VCAT receiver 134 is generally a pathterminating device. In general, as previously mentioned, VCAT group 106includes “N” member or paths. VCAT group 106 is shown as including fourpaths, namely paths 144, 148, 152, 156. Path 144 passes through networkelements 140 a, 140 b, and includes links 144 a-c. Path 148 also passesthrough network elements 140 a, 140 b, but includes links 148 a-c. Path152 includes links 152 a, 152 b, and passes through a network element140 c, while path 156 includes links 156 a, 156 b, and passes through anetwork element 140 d.

Each path 144, 148, 152, 156 may be identified by a sequence number.Sequence numbers typically range from zero to “N−1”. As VCAT group 106includes four paths, sequence numbers associated with VCAT group 106range from zero to three. Typically, sequence numbers associated withpaths 144, 148, 152, 156 must be verified by VCAT receiver 134. That is,VCAT receiver 134 verifies that the sequence numbers associated withpaths 144, 148, 152, 156 match expected sequence numbers stored withinVCAT receiver 134. VCAT receiver 134 uses the sequence numbers toreconstruct an overall data stream that was sent on paths 144, 148, 152,156.

The ability to verify sequence numbers or, more specifically, toidentify sequence mismatch defects associated with a VCAT group iscrucial to ensure the integrity of the VCAT group. When a VCAT group isconfigured, a person responsible configuring the VCAT group generallymust have a detailed understanding of the hardware capabilities of aVCAT receiver associated with the VCAT group, as that person typicallyspecifies the expected sequence numbers in the VCAT receiver. Specifyingexpected sequence numbers in a VCAT receiver may be a time-consumingtask, as the hardware capabilities of the VCAT receiver are oftencomplicated to comprehend.

In some implementations, expected sequence numbers that are used toidentify sequence mismatch defects are programmed into a VCAT receiverdynamically based on sequence numbers received, for example, during apolling cycle associated with the VCAT receiver. Such programming mayoccur using software or using hardware which programs expected sequencenumbers in real-time. Generally, a static VCAT receiver has provisioned,expected sequence numbers. These expected sequence numbers may besupplied by network elements that are in communication with the staticVCAT receiver either explicitly or implicitly, e.g., derived from aparameter provided by the network elements. A dynamic VCAT receivertypically does not have any provisioned, expected sequence numbers. Fora static VCAT receiver, an issue arises regarding the accuracy ofreceived sequence numbers that are used as expected sequence numbers. Ifthe received sequence numbers are invalid, e.g., either greater than“N−1” for an “N” member VCAT group or duplicated, using invalid sequencenumbers as expected sequence compromises the integrity of the VCAT groupand, hence, the overall network of which the VCAT group is a part.

Therefore, what is needed is a method and an apparatus which allowssequence mismatch defects to be accurately and efficiently detected.That is, what is desired is a system which enables sequence mismatchdefects associated with one or more members of a VCAT group to beidentified dynamically.

SUMMARY OF THE INVENTION

The present invention relates to identifying sequence mismatch defectsassociated with members of a virtual concatenation (VCAT) group.According to one aspect of the present invention, a method for detectingsequence mismatch defects associated with a VCAT group thatsubstantially terminates at a VCAT sink includes obtaining a first setof sequence numbers associated with the VCAT group at a first time, anddetermining whether a first sequence number of the first set isdefective. Determining whether the first sequence number is defectiveincludes determining whether the first sequence number is invalid. Themethod also includes identifying the first sequence number as having asequence mismatch defect if the first sequence number is determined tobe invalid.

In one embodiment, the first sequence number is determined to be invalidif it is either a duplicate of a second sequence number of the firstset, or if it is out of bounds. In such an embodiment, the firstsequence number may also be determined to be invalid if it does notmatch sequence numbers stored in a second set of sequence numbers thatwas obtained during a previous polling cycle.

If a VCAT sink is configured to identify sequence mismatch defects bycomparing current sequence numbers obtained from a VCAT group againstpreviously obtained sequence numbers, the VCAT sink may verify thesequence numbers efficiently and effectively. Further, the need to useexpected sequence numbers stored in the VCAT sink to identify sequencemismatch defects is substantially eliminated. If there are discrepanciesbetween the current sequence numbers and the previous sequence numbers,there may be sequence mismatch defects associated with the currentsequence numbers. For VCAT sinks in which expected sequence numbers arestored, information pertaining to current sequence numbers andpreviously obtained sequence numbers may be used to allows the expectedsequence numbers to be accurately updated.

According to another aspect of the present invention, a sink associatedwith a VCAT group includes a processor, a memory that includes a firstdata structure such as an array, and devices that cooperate with theprocessor to obtain current sequence numbers associated with the VCATgroup. The devices also store the current sequence numbers into thefirst data structure and identify sequence mismatch defects associatedwith the current sequence numbers. The devices that identify sequencemismatch defects associated with the current sequence numbers identifyones of the current sequence numbers that are out of bounds and ones ofcurrent sequence numbers that are duplicates.

In one embodiment, the devices also store previous sequence numbersassociated with the VCAT group into a second data structure in thememory. In such an embodiment, the devices may also compare the set ofcurrent sequence numbers against the set of previous sequence numbers toidentify sequence mismatch defects. In another embodiment, the devicesmay be either or both hardware devices and program code devices that theprocessor may cause to execute.

According to another aspect of the present invention, a method forupdating expected sequence numbers stored in a memory of a VCAT receiverincludes obtaining a set of current sequence numbers associated with theVCAT group, as well as determining whether the set of current sequencenumbers associated with the VCAT group does not include a first invalidsequence number. If the set of current sequence numbers is determinednot to include a first invalid sequence number, the method involvesdetermining if a set of previous sequence numbers associated with theVCAT group includes at least one invalid sequence number. Finally, themethod includes replacing the expected sequence numbers with the set ofcurrent sequence numbers if it is determined that the set of previoussequence numbers includes at least one invalid sequence number.

In one embodiment, the method also includes setting a first variable toa first value to indicate that the set of current sequence numbersincludes substantially only valid sequence numbers if the set of currentsequence numbers does not include the invalid sequence numbers. If theset of previous sequence numbers includes at least one invalid sequencenumber, the first variable is such that it was previously set to asecond value, e.g., a value that indicated that the set of previoussequence numbers includes at least one invalid sequence number.

These and other advantages of the present invention will become apparentupon reading the following detailed descriptions and studying thevarious figures of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by reference to the followingdescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1A is a block diagram representation of a virtual concatenation(VCAT) group within a network.

FIG. 1B is a diagrammatic representation of a VCAT source and a VCATreceiver associated with a VCAT group with multiple members, i.e., VCATgroup 106 of FIG. 1A.

FIG. 2 is a block diagram representation of a VCAT receiver inaccordance with one embodiment of the present invention.

FIG. 3 is a diagrammatic representation of a current array that ismarked to indicate each detected sequence mismatch defect as well as anold array against which the current array is compared in accordance withan embodiment of the present invention.

FIGS. 4A and 4B are a process flow diagram which illustrates one methodof detecting sequence mismatch defects in accordance with an embodimentof the present invention.

FIG. 5 is a block diagram representation of a VCAT receiver that storesexpected sequence numbers in accordance with an embodiment of thepresent invention.

FIG. 6 is a process flow diagram which illustrates one method ofupdating stored expected sequence numbers in accordance with anembodiment of the present invention.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The ability to accurately and efficiently identify sequence mismatchdefects associated with virtual concatenation (VCAT) groups inSynchronous Optical Network (SONET) and Synchronous Digital Hierarchy(SDH) transport networks allows the integrity of the VCAT groups to bemaintained. If sequence mismatch defects are efficiently identified,proper steps may be taken to address the sequence mismatch defects in atimely manner. Hence, the overall performance of the transport networksof which the VCAT groups are a part may be improved.

Enabling a VCAT receiver or sink to identify sequence mismatch defectsthrough a comparison of current sequence numbers against previouslyobtained sequence numbers allows the VCAT receiver to effectively becomea dynamic receiver. If there are discrepancies between the currentsequence numbers and the previous sequence numbers, it may be determinedthat there are sequence mismatch defects. For VCAT receivers which storeexpected sequence numbers, information pertaining to current sequencenumbers and previously obtained sequence numbers may be used to bothfacilitate the identification of the expected sequence numbers and toincrease the likelihood that the expected sequence numbers are valid.For instances in which expected sequence numbers are required by theVCAT receiver, such expected sequence numbers may be derived fromreceived sequence numbers, and may not need to be known in advance.

Current sequence numbers and previously obtained sequence numbers maygenerally be stored in memory within a VCAT receiver. In one embodiment,both the current sequence numbers and the previously obtained sequencenumbers may be stored at least temporarily in arrays within memoryassociated with the VCAT receiver. Current sequence numbers may beobtained periodically, as for example every few milliseconds or everypolling cycle. Whenever the contents are updated in the array in whichthe current sequence numbers are to be stored, the previous contents ofthat array may be copied into the array in which previously obtainedsequence numbers are to be stored.

FIG. 2 is a block diagram representation of a VCAT receiver inaccordance with one embodiment of the present invention. A VCAT receiveror sink 202 is a device or path terminating element that is arranged toeffectively be a terminating point or node for members or paths 206 of aVCAT group with “N” receiving members. VCAT receiver 202 is alsoarranged to substantially reconstruct a data stream by collecting datareceived from any or all members or paths 206. VCAT receiver 202 mayeither be configured with information relating to how many componentsare associated with the VCAT group, or may be arranged to be informed ofhow many components are in the VCAT group.

Members or paths 206 may generally be SONET paths or SDH paths. Membersor paths 206 may effectively be in communication with VCAT receiver 202via a network interface 210. It should be appreciated that networkinterface 210 may enable data to be received by VCAT receiver 202 andalso enable data to be set by VCAT receiver 202.

VCAT receiver 202 includes sequence mismatch devices 220 which, in oneembodiment, are hardware devices that may cooperate with a processor 224to allow sequence mismatch defects associated with members or paths 206to be identified. The hardware devices may include various electricalcomponents such as integrated circuits, e.g., application specificintegrated circuits, that are arranged to identify sequence mismatchdefects. It should be appreciated, however, that sequence mismatchdevices 220 may also include software or program code devices stored ona computer-readable medium which may be executed by processor 224.Sequence mismatch devices 220 may obtain the sequence numbers associatedwith members or paths 206, and cause a current array 230 in a memory 228to store the obtained sequence numbers. Sequence mismatch defects may beidentified by sequence mismatch devices 220 during processing of thecontents of current array 230, as well as processing of the contents ofa previous or old array 234 in memory 228 that is arranged to storeprevious sequence numbers. The contents of previous array 234 aretypically sequence numbers associated with the VCAT group that werepreviously obtained, as for example during the immediately precedingpolling in which an attempt was made to identify sequence mismatchdefects.

Sequence mismatch devices 220 are generally arranged to mark currentarray 230 to indicate the elements within current array 230 whichcontain sequence mismatch defects. Current array 230 may be marked whenmarkers or values are placed into an array or column of current array230 that is appropriate for identifying particular sequence numbersstored in another row or column, respectively, as having a sequencemismatch defect. A sequence mismatch defect, or a loss of sequence, mayinvolve an out of bounds sequence number, or a sequence number that ishigher than “N−1” for a VCAT group with “N” receiving members or lowerthan “0.” A sequence mismatch defect may also involve duplicate sequencenumbers, as well as sequence numbers that do not match those stored inprevious array 234.

In general, a VCAT receiver for a VCAT group with “N” receiving membersexpects received sequence numbers to be a member of the set of positiveinteger numbers between “0” and “N−1”. Any sequence number that is notin the set of positive integers between “0” and “N−1” is considered tobe out of bounds. Hence, sequence numbers that are either positiveintegers that are greater than or equal to “N” for a VCAT group with “N”receiving members or are negative integers may be considered to be outof bounds.

Referring next to FIG. 3, the marking of sequence mismatch defects in acurrent array or, more generally, a data structure that containssequence number inputs from a VCAT group with “N” receiving members,will be described in accordance with an embodiment of the presentinvention. A current array 330 includes an area 364 in which sequencenumbers associated with a VCAT group with “N” receiving members arelocated. For ease of discussion, a VCAT group with “N” receiving memberswill generally be described as a VCAT group with “N” members. It shouldbe appreciated that such a VCAT group, i.e., a VCAT group with “N”members, includes “N” receiving members and may generally include anynumber of transmitting members. If out of bounds sequence numbers orduplicate sequence numbers are found within current array 364, suchsequence numbers are marked as having a sequence mismatch defect. Ingeneral, sequence mismatch defects may be identified by placing a bit orbits in an area 360. By way of example, if areas 360, 364 are columns, asequence mismatch defect indicator may be placed within column 360 inthe same row in which mismatched sequence number is stored within column364.

A sequence number 370 is an out of bounds sequence number, as “N+3” is alarger number than the maximum permissible sequence number, i.e.,sequence number “N−1”, associated with the VCAT group with N members. Ingeneral, “N” represents the maximum number of members within a VCATgroup, and may vary widely. By way of example, for higher-order VCAT,“N” may have a value of approximately 256, whereas for lower-order VCAT,“N” may have a value of approximately 64. Typically, “N” has a valuethat falls in the range between 1 and 256.

As sequence number 370 is out of bounds, an indication 380 a thatsequence number 370 has a sequence mismatch defect is placed in area360. Sequence numbers 368 are duplicates and, as a result, are eachidentified as having sequence mismatch defects with indications 380 b,380 c in area 360. Though sequence number 372 is neither out of boundsnor a duplicate of any other sequence number stored in area 364,sequence number 372 does not match any sequence number in a previousarray 334 that is arranged to store sequence numbers obtainedpreviously, e.g., during a previous polling cycle associated with a VCATreceiver such as receiver 202 of FIG. 2. Hence, sequence number 372 ismarked in area 360 with an indication 380 d that is arranged to identifysequence number 372 as having a sequence mismatch defect.

In the described embodiment, sequence numbers that are out of boundssuch as sequence number 370 may be marked the same way as duplicatesequence numbers 368. That is, sequence mismatch defects may be markedso as not to differentiate between different types of sequence mismatchdefects. However, it should be appreciated that sequence numbers thatare out of bounds may instead be marked differently from sequencenumbers that are duplicates. Similarly, although sequence numbers suchas sequence number 372 that does not match sequence numbers stored inprevious or old array 334 may be marked differently than those sequencenumbers that are out of bounds or duplicates, as shown, substantiallyall sequence mismatch defects may be indicated using the same marker.

With reference to FIGS. 4A and 4B, one method of detecting sequencemismatch defects with a dynamic sink or receiver will be described inaccordance with an embodiment of the present invention. A process 400 ofdetecting or identifying sequence mismatch defects begins at step 404 inwhich a current array is initialized. A current array, which may bestored in a memory of a VCAT receiver, is arranged to hold the sequencenumbers of current members or paths in a VCAT group. Initializing thecurrent array may involve setting the values of an empty array, as forexample to values of zero, if the array has not been used.Alternatively, if the current array contains sequence numbers associatedwith the VCAT group, initializing the current array may includesubstantially copying sequence numbers associated with the VCAT groupinto another array, e.g., a previous or old array, and then setting thevalues in the current array to values of zero.

Once the current array is initialized, the sequence number for eachmember of the VCAT group is extracted or otherwise obtained in step 408.Components of the VCAT receiver, as for example sequence mismatchdevices 220 of FIG. 2, may be arranged to allow the sequence number foreach member of the VCAT group to be extracted. After the sequencenumbers are extracted, each extracted sequence number is stored into thecurrent array in step 412. Then, in step 416, the stored sequencenumbers may be sorted. That is, the contents of the current array may besorted such that the sequence numbers are effectively in numericalorder, e.g., either ascending or descending. The sorting of sequencenumbers in numerical order generally facilitates the processing of thesequence numbers.

A determination is made in step 420 regarding whether any of thesequence numbers stored in the current array are out of bounds orduplicates. Determining whether any of the sequence numbers stored inthe current array are out of bounds or duplicates generally entailsdetermining whether any of the sequence numbers are illegal or invalid.As previously mentioned, sequence numbers typically fall between zeroand “N−1” for a VCAT group that includes “N” members. Hence, a sequencenumber that is stored in the current array may be considered to be outof bounds if that sequence number has a value that is greater than“N−1.”

If it is determined in step 420 that none of the sequence numbers areout of bounds or duplicates, i.e., that all of the sequence numbers arein bounds and non-duplicated, the indication is that there are nosequence mismatch defects associated with the sequence numbers stored inthe current array. Accordingly, none of the sequence numbers stored inthe current array are marked as having sequence mismatch defects, andprocess flow moves from step 420 to step 428 in which the unmarkedsequence numbers stored in the current array are compared to thesequence numbers stored in a previous, or old, array.

Once the sequence numbers stored in the current array are compared tothe sequence numbers stored in the previous array, it is determined instep 432 whether there are any sequence numbers that are differentbetween the current array and the previous array. That is, adetermination is made regarding whether the sequence numbers stored inthe current array match the sequence numbers stored in the previousarray. If the determination is that substantially all of the sequencenumbers stored in the current array match the sequence numbers stored inthe previous array, then the process of identifying sequence mismatchdefects is completed.

Alternatively, if it is determined in step 432 that there aredifferences between the sequence numbers stored in the current array andthe sequence numbers stored in the previous array, the indication isthat there is at least one sequence mismatch defect associated with thecurrent array. As such, in step 436, any sequence numbers in the currentarray that are different from the sequence numbers in the previous arrayare marked as having a sequence mismatch defect. After the sequencenumbers in the current array are marked as appropriate, the process ofidentifying sequence mismatch defects is completed.

Returning to step 420, if it is determined that there is at least onesequence number in the current array that is either out of bounds orduplicated, the indication is that there is at least one sequencemismatch defect associated with the current array and, hence, the VCATgroup for which sequence numbers are stored in the current array.Accordingly, process flow moves from step 420 to step 424 in which anyout of bounds sequence number or duplicate sequence number is marked ashaving a sequence mismatch defect. In one embodiment, a column of thecurrent array may be arranged to be marked to indicate which sequencenumbers stored in the current array have sequence mismatch defects. Oncethe sequence mismatch defects are marked, the sequence numbers stored inthe current array that are unmarked are compared to sequence numbersstored in a previous array in step 428.

In some systems, VCAT receivers are such that expected sequence numbersare stored on the VCAT receivers. Expected sequence numbers generallycorrespond to the sequence numbers that are expected to correspond to aVCAT group that terminates at the VCAT receiver. Such VCAT receivers mayhave expected sequence numbers programmed therein, either in hardware orin software. FIG. 5 is a block diagram representation of a VCAT receiverin which expected sequence numbers are stored in accordance with oneembodiment of the present invention. A VCAT receiver 502 includessequence mismatch devices 520 and a processor 524 that are arranged tocooperate to identify sequence mismatch defects associated with paths506 associated with a VCAT group that terminates at VCAT receiver 502.Typically, there are “N” paths 506 that correspond to a VCAT group with“N” members. Paths 506 typically enter VCAT receiver 528 via a networkinterface 510.

A memory 528 of is arranged to contain a current array 530 that holdsthe most current sequence numbers associated with paths 506. An oldarray 534, which is also stored in memory 534, is arranged to containpreviously obtained sequence numbers associated with paths 506. Expectedsequence numbers 544 are also stored in memory 528. Expected sequencenumbers 544, which may be stored in substantially any suitable datastructure, are generally the sequence numbers that paths 506 areexpected to have.

The ability to update expected sequence numbers 544 enables expectedsequence numbers 544 to be relatively accurate. In other words, asexpected sequence numbers 544 that are substantially programmed intoVCAT receiver 502 when VCAT receiver 502 is effectively initialized maynot be entirely accurate, the ability to update expected sequence number544 when information that may be more accurate or up-to-date isavailable. Information that is more accurate may correspond to sequencenumbers that are stored in current array 530 and old array 534. Forexample, if current array 530 and old array 534 contain substantiallythe same sequence numbers, then those sequence numbers may be consideredto accurately reflect the sequence numbers that may be expected.

Referring next to FIG. 6, one method of updating expected sequencenumbers that are stored within a VCAT receiver will be described inaccordance with an embodiment of the present invention. A process ofupdating expected sequence numbers 600 begins at step 604 in which acurrent array of sequence numbers is processed. Processing a currentarray of sequence numbers may include writing sequence numbers into anarray, as for example using sequence mismatch devices of a VCATreceiver, sorting the sequence numbers stored within the current array,and identifying any sequence mismatch defects in the current array. Onemethod of processing a current array to identify sequence mismatchdefects is described above with respect to FIGS. 4A and 4B.

After the current array is processed, a determination is made in step608 as to whether there are any sequence mismatch defects associatedwith the sequence numbers stored in the current array. If it isdetermined that there are sequence mismatch defects, then a logicalvariable is set to a true value in step 612 to indicate that there aresequence mismatch defects associated with the most current sequencenumbers, i.e., the sequence numbers stored in the current array. Such alogical variable may be a logical OR, in one embodiment. Once thelogical variable is set to a true value or, more generally, is set toindicate that the current array has sequence mismatch defects, theprocess of updating expected sequence numbers is terminated.

If the determination in step 608 is that there are no sequence mismatchdefects associated with the sequence numbers stored in the currentarray, the previous or existing value of the logical variable that isused to indicate whether a current array has sequence mismatch defectsis noted in step 616. The previous value of the logical variablegenerally indicates whether there are sequence mismatches in an oldarray, as for example old array 534 of FIG. 5. After the previous valueof the logical variable is noted, the logical variable is set in step620 to indicate that the current array does not have sequence mismatchdefects. In the described embodiment, setting the logical variable toindicate that the current array does not have sequence mismatch defectsincludes setting the logical variable to a false value.

From step 620, process flow moves to step 624 in which it is determinedwhether the previous value of the logical variable was true. That is, itis determined in step 624 whether the old array contained sequencemismatch defects when it was processed to identify sequence mismatchdefects. If it is determined that the previous value of the logicalvariable was not true, then the indication is that the sequence numbersare relatively stable. Hence, the expected sequence values stored withinthe VCAT receiver are considered to be relatively accurate. As such, theprocess of updating expected sequence numbers is terminated.

Alternatively, if it is determined in step 624 that the previous valueof the logical variable was true, then the implication is that thesequence numbers stored in the current array are likely to be theexpected sequence numbers and, further that the current expectedsequence numbers are likely to be outdated. Accordingly, in step 628,the expected sequence numbers are updated or reset within the VCATreceiver using the sequence numbers stored in the current array. Theexpected sequence numbers are, hence, effectively set dynamically, e.g.,using software code devices. Once the expected sequence numbers areupdated, the process of updating expected sequence numbers is completed.

Although only a few embodiments of the present invention have beendescribed, it should be understood that the present invention may beembodied in many other specific forms without departing from the spiritor the scope of the present invention. By way of example, while sequencenumbers have been described as being stored in an array for comparisonpurposes, the sequence numbers may be stored in substantially anysuitable data structure. That is, arrays are but one example of a datastructure in which current and previous sequence numbers may be stored.In addition, in lieu of storing sequence numbers in a data structure,sequence numbers may instead be stored in temporary variables within amemory associated with a VCAT receiver.

As discussed above, in one embodiment, a method for detecting sequencemismatch defects may be performed using substantially only hardwarecomponents. For example, such a method may be implemented using anapplication specific integrated circuit (ASIC) or using afield-programmable gate array (FPGA).

A sequence number has generally been described as being invalid orillegal when that sequence number is either out of bounds or duplicated.That is, a sequence mismatch defect has been described as being detectedwhen a sequence number is out of bounds or duplicated. It should beunderstood, however, that a sequence number is not limited to beinginvalid only if the sequence number is out of bounds or duplicated.

While the VCAT sequence mismatch defect detection of the presentinvention has been described as being suitable for use in either a SONETtransport network or an SDH transport network, the VCAT sequencemismatch defect detection described above may generally be implementedwithin any suitable network. Further, although a VCAT sequence mismatchdefect detection scheme may be a hardware oriented implementation, sucha scheme may also be implemented as a combination hardware and softwareimplementation, or as a substantially software implementation.

A VCAT receiver may be a component of a network element such as a routeror a computing system. If a VCAT receiver is a component of a computingsystem, the VCAT receiver may cooperate with other components of thecomputing system to perform sequence mismatch defect detection. Othercomponents of the computing system may include, but are not limited to,a processor, a random access memory, a read only memory, a networkinterface, input devices, and display devices.

Generally, VCAT groups with N members may symmetric and bidirectional.It should be appreciated, however, that VCAT groups may instead byasymmetric and unidirectional. In one embodiment, a VCAT group mayinclude both symmetric and asymmetric members. The present inventiondescribes the behavior of a VCAT receiver that terminates “N” receivingmembers of a VCAT group, though the number of transmitting members ofthe VCAT group may or may not be “N”. For a symmetric VCAT group, thereare “N” receiving members and “N” transmitting members. In an asymmetricVCAT group, there may be “N” receiving members and substantially anynumber of transmitting members.

The steps associated with the processes associated with sequencemismatch defect detection may vary widely. Steps may be added, removed,altered, and reordered without departing from the spirit or scope of thepresent invention. For example, the step of sorting the contents of anarray to facilitate checking for sequence numbers that are duplicates orout of bounds may be removed or replaced without departing from thespirit or the scope of the present invention. In other words, sortingthe contents of an array may be optional.

Additionally, in one embodiment, the identification of sequence mismatchdefects may occur substantially without comparing the contents of acurrent array against the contents of an old array. That is, sequencemismatch defects may be identified by checking for sequence numbers thatare out of bounds as well as sequence numbers that are duplicates amongthe sequence numbers stored in a current array, and without checking tosee if the sequence numbers stored in the current array match thesequence numbers stored in an old array. In such an embodiment, it maynot be necessary to maintain an old array. Therefore, the presentexamples are to be considered as illustrative and not restrictive, andthe invention is not to be limited to the details given herein, but maybe modified within the scope of the appended claims.

1. A method for detecting sequence mismatch defects associated with avirtual concatenation (VCAT) group, the VCAT group being associated witha VCAT sink, the method comprising: obtaining a first set of sequencenumbers from the VCAT group at a first time; determining whether a firstsequence number of the first set of sequence numbers is invalid; andidentifying the first sequence number as having a sequence mismatchdefect if it is determined that the first sequence number is invalid. 2.The method of claim 1 wherein the first set of sequence numbers includesa second sequence number, and determining whether the at least firstsequence number is invalid includes determining whether the firstsequence number and the second sequence number are the same.
 3. Themethod of claim 2 wherein if it is determined that the first sequencenumber and the second sequence number are the same, the method furtherincludes identifying both the first sequence number and the secondsequence number as having sequence mismatch defects.
 4. The method ofclaim 1 wherein determining whether the first sequence number is invalidincludes determining whether the first sequence number is out of bounds.5. The method of claim 4 wherein the VCAT group includes N members, anddetermining whether the first sequence number is out of bounds includesdetermining whether the first sequence number exceeds a value of oneless than N.
 6. The method of claim 1 wherein the VCAT sink includes amemory, the method further including: storing the first set of sequencenumbers into a first array, the first array being arranged in thememory.
 7. The method of claim 1 further including: obtaining a secondset of sequence numbers associated with the VCAT group at a second time,the second time being before the first time, the second set of sequencenumbers being obtained from the VCAT group.
 8. The method of claim 7wherein determining whether the first sequence number of the first setof sequence numbers is invalid includes comparing the first sequencenumber against the second set of sequence numbers to determine if thefirst sequence number matches any of the second set of sequence numbers.9. The method of claim 8 wherein if it is determined that the firstsequence number does not match any of the second set of sequencenumbers, the first sequence number is determined to be invalid.
 10. Themethod of claim 7 further including: storing the first set of sequencenumbers into a first array, the first array being arranged in a memoryof the VCAT sink; and storing the second set of sequence numbers into asecond array, the second array being arranged in the memory.
 12. Anapparatus suitable for use in a transport network, the device beingarranged as a sink associated with a virtual concatenation (VCAT) group,the apparatus comprising: a processor; a memory, the memory beingarranged to include a first data structure; and devices arranged tocooperate with the processor to obtain a set of current sequence numbersassociated with the VCAT group, the devices further being arranged tostore the set of current sequence numbers into the first data structureand to identify sequence mismatch defects associated with the set ofcurrent sequence numbers, wherein the devices that identify sequencemismatch defects associated with the set of current sequence numbersidentify current sequence numbers of the set of current sequence numbersthat are out of bounds and current sequence numbers of the set ofcurrent sequence numbers that are duplicates.
 13. The apparatus of claim12 wherein the memory is further arranged to include a second datastructure, and the devices are further arranged to store a set ofprevious sequence numbers associated with the VCAT group into the seconddata structure and to compare the set of current sequence numbersagainst the set of previous sequence numbers to identify sequencemismatch defects.
 14. The apparatus of claim 1 further including:sorting the first set of sequence numbers.
 15. A computer programproduct for detecting sequence mismatch defects associated with avirtual concatenation (VCAT) group, the VCAT group being associated witha VCAT sink, the computer program product comprising: code devicesarranged to cause a set of current sequence numbers associated with theVCAT group to be obtained; code devices further arranged to cause theset of current sequence numbers to be stored into a first datastructure; code devices arranged to cause sequence mismatch defectsassociated with the set of current sequence numbers to be identified,wherein the code devices that cause sequence mismatch defects associatedwith the set of current sequence numbers to be identified include codedevices that cause current sequence numbers of the set of currentsequence numbers that are out of bounds and current sequence numbers ofthe set of current sequence numbers that are duplicates to beidentified; and a computer-readable medium that stores the code devices.16. An apparatus suitable for detecting sequence mismatch defectsassociated with a virtual concatenation (VCAT) group, the VCAT groupbeing in communication with the apparatus, the apparatus comprising:means for obtaining a first set of sequence numbers from the VCAT groupat a first time; means for determining whether a first sequence numberof the first set of sequence numbers is defective; and means foridentifying the first sequence number as having a sequence mismatchdefect if it is determined that the first sequence number is defective.17. The apparatus of claim 16 wherein the first set of sequence numbersincludes a second sequence number, and the means for determining whetherthe at least first sequence number is defective include means fordetermining whether the first sequence number and the second sequencenumber are the same.
 18. The apparatus of claim 16 wherein the means fordetermining whether the first sequence number is defective include meansfor determining whether the first sequence number is out of bounds. 19.The apparatus of claim 16 further including: a memory; and means forstoring the first set of sequence numbers into a first array, the firstarray being arranged in the memory.
 20. The apparatus of claim 16further including: means for obtaining a second set of sequence numbersassociated with the VCAT group at a second time, the second time beingbefore the first time, the second set of sequence numbers being obtainedfrom the VCAT group.
 21. The apparatus of claim 20 wherein the means fordetermining whether the first sequence number of the first set ofsequence numbers is defective include means for comparing the firstsequence number against the second set of sequence numbers to determineif the first sequence number matches any of the second set of sequencenumbers.
 22. The apparatus of claim 20 further including: a memory;means for storing the first set of sequence numbers into a first array,the first array being arranged in the memory; and means for storing thesecond set of sequence numbers into a second array, the second arraybeing arranged in the memory.
 23. A method for updating expectedsequence numbers stored in a memory of a virtual concatenation (VCAT)receiver, the expected sequence numbers being associated with a VCATgroup that is in communication with the VCAT receiver, the methodcomprising: obtaining a set of current sequence numbers associated withthe VCAT group; determining whether the set of current sequence numbersassociated with the VCAT group does not include a first invalid sequencenumber; determining whether a set of previous sequence numbersassociated with the VCAT group includes at least one invalid sequencenumber if it is determined that the set of current sequence number doesnot include the first invalid sequence number; and replacing theexpected sequence numbers with the set of current sequence numbers if itis determined that the set of previous sequence numbers includes the atleast one invalid sequence number.
 24. The method of claim 23 furtherincluding: setting a first variable to a first value to indicate thatthe set of current sequence numbers includes substantially only validsequence numbers if it is determined that the set of current sequencenumbers does not include the invalid sequence numbers.
 25. The method ofclaim 24 wherein the first variable is previously set to a second valueto indicate that the set of previous sequence numbers includes the atleast one invalid sequence number.
 26. The method of claim 25 furtherincluding wherein determining whether the set of previous sequencenumbers includes the at least one invalid sequence number includesdetermining whether the first variable was previously set to the secondvalue.
 27. The method of claim 23 wherein determining whether the set ofcurrent sequence numbers does not include the first invalid sequencenumber includes determining whether the set of current sequence numbersincludes substantially only in bounds sequence numbers andnon-duplicated sequence numbers.
 28. The method of claim 27 whereindetermining whether the set of current sequence numbers does not includethe first invalid sequence number further includes determining whetherthe set of current sequence numbers does not include any sequence numberthat is not also included in the set of previous sequence numbers. 29.The method of claim 23 further including: sorting the set of currentsequence numbers.
 30. An apparatus suitable for use in a transportnetwork, the device being arranged as a sink associated with a virtualconcatenation (VCAT) group, the apparatus comprising: means forobtaining a set of current sequence numbers associated with the VCATgroup; means for determining whether the set of current sequence numbersassociated with the VCAT group does not include a first invalid sequencenumber; means for determining whether a set of previous sequence numbersassociated with the VCAT group includes at least one invalid sequencenumber if it is determined that the set of current sequence numbers doesnot include the first invalid sequence number; and means for replacingthe expected sequence numbers with the set of current sequence numbersif it is determined that the set of previous sequence numbers includesthe at least one invalid sequence number.
 31. The apparatus of claim 30further including: means for setting a first variable to a first valueto indicate that the set of current sequence numbers includessubstantially only valid sequence numbers if it is determined that theset of current sequence numbers does not include the invalid sequencenumbers.
 32. The apparatus of claim 31 wherein the first variable ispreviously set to a second value to indicate that the set of previoussequence numbers includes the at least one invalid sequence number,wherein the means for determining whether the set of previous sequencenumbers includes the at least one invalid sequence number include meansfor determining whether the first variable was previously set to thesecond value.
 33. The apparatus of claim 30 wherein the means fordetermining whether the set of current sequence numbers does not includethe first invalid sequence number include means for determining whetherthe set of current sequence numbers includes substantially only inbounds sequence numbers and non-duplicated sequence numbers.
 34. Theapparatus of claim 33 wherein the means for determining whether the setof current sequence numbers does not include the first invalid sequencenumber further includes means for determining whether the set of currentsequence numbers does not include any sequence number that is not alsoincluded in the set of previous sequence numbers.
 35. An apparatussuitable for use in a transport network, the device being arranged as asink associated with a virtual concatenation (VCAT) group, the apparatuscomprising: a processor; a memory, the memory being arranged to storeexpected sequence numbers associated with the VCAT group; and devicesarranged to cooperate with the processor to obtain a set of currentsequence numbers associated with the VCAT group, the devices furtherbeing arranged to determine whether the set of current sequence numbersdoes not include a first invalid sequence number, determine whether aset of previous sequence numbers associated with the VCAT group includesat least one invalid sequence number if it is determined that the set ofcurrent sequence numbers does not include the first invalid sequencenumber, and replace the expected sequence numbers with the set ofcurrent sequence numbers if it is determined that the set of previoussequence numbers includes the at least one invalid sequence number. 36.The apparatus of claim 35 wherein the devices are further arranged toset a first variable to a first value to indicate that the set ofcurrent sequence numbers includes substantially only valid sequencenumbers if it is determined that the set of current sequence numbersdoes not include the invalid sequence numbers.
 37. The apparatus ofclaim 36 wherein the first variable is previously set to a second valueto indicate that the set of previous sequence numbers includes the atleast one invalid sequence number, and wherein the devices thatdetermine whether the set of previous sequence numbers includes the atleast one invalid sequence number include devices that determine whetherthe first variable was previously set to the second value.
 38. Acomputer program product for detecting sequence mismatch defectsassociated with a virtual concatenation (VCAT) group, the VCAT groupbeing associated with a VCAT sink, the computer program productcomprising: code devices that cause a set of current sequence numbersassociated with the VCAT group to be obtained; code devices that cause adetermination of whether the set of current sequence numbers does notinclude a first invalid sequence number; code devices that cause adetermination of whether a set of previous sequence numbers associatedwith the VCAT group includes at least one invalid sequence number if itis determined that the set of current sequence numbers does not includethe first invalid sequence number; code devices that cause the expectedsequence numbers to be replaced with the set of current sequence numbersif it is determined that the set of previous sequence numbers includesthe at least one invalid sequence number; and a computer-readable mediumthat stores the code devices.